In-line lens manufacturing

ABSTRACT

A method of hard coating a lens includes maintaining a dip tank at a temperature T D , wherein the dip tank includes a liquid including a primer or a hard coat solution. The lens is dried and heated to a temperature T L . The lens is dipped into the dip tank wherein T L  is within 20 degrees F. of T D .

CROSS REFERENCE

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 10/430,035 filed May 6, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to lens manufacturing and moreparticularly to systems and methods for dipping lenses for a high yieldautomated process.

2. Description of the Related Art

Prescription lenses require customization for individual users.Traditionally, prescription lenses were ground from glass based on theprescription and the facial dimensions of the wearer. This is often atime consuming and labor intensive process, which increases costs. Inaddition, glass can crack or shatter making it difficult to maintain andeven creating the possibility for injury.

With improvements in plastics molding, lenses began being fabricated byprocesses, such as injection molding and compression molding. Plasticmaterials, such as polycarbonate, provide a plurality of advantages overglass lenses. Molding processes are typically automated and are rapidlyperformed. In addition, polycarbonate is lighter in weight than glassand does not shatter.

One disadvantage of employing plastic lenses is that plastic is softcompared to glass and, as such, is not sufficiently resistant toscratching. This problem is addressed by coating the lens with a hardcoating layer using a process commonly referred to as dipcoating.Conventional dipcoating processes typically require a plurality ofcleaning steps after the lens is cooled to room temperature. Forexample, after cooling the lens from the mold, the lens is dipped in oneor more solvent baths followed by detergent baths to ensure the removalof oils and dirt. Cooling the lens to room temperature is required toprevent solvents and detergents from attacking the lens material.Solvents are more likely to cause damage to the lens at elevatedtemperatures. Lenses are often air cooled, which makes the lensvulnerable to dirt or dust accumulation on the lens. This is increasedby static charge which can build up on the lens. One prior art techniqueemploys an alcohol bath to cool and destaticize the lens. However, thisprocess uses alcohol which must then be air dried to permit the alcoholto evaporate. The evaporation time gives air borne particles a chance tocollect on the lens. Additionally, although very volatile, alcoholresidue may remain on the lens after it has dried, and may require anadditional cleaning step or steps.

After being cooled to room temperature either in air or in liquid, thelenses are detergent dipped which is followed by one or more additionalsolvent (rinse) bath dips. The lens is then dried over a period of timein a filtered environment, which attempts to eliminate particles fromthe ambient environment. When completely dried, the lenses are initiatedinto the dip coating process. The dipcoat, once cured, provides scratchresistance for the lens.

The conventional dipcoating process yields a high number of lenses, butis complex and often requires a large number of process steps, some ofwhich are long in duration. Drying times and cleaning stations sometimesbecome bottlenecks to an assembly line, but are needed since solventstreaks are one of the most common causes of rejecting lenses. Inaddition, conventional processes require that the lens be cooled,usually to room temperature, prior to the onset of the dipcoatingprocess. This is typically regarded as necessary for promoting adhesionbetween the hard coat material and the lens and in preventing solventattack of the lens material.

Referring to FIG. 1, two prior art dip coating techniques arecomparatively shown. Lines drawn between states in FIG. 1 approximateeach process. Although lines are employed, the lines are used torepresent any relationship, e.g., exponential decay or polynumericrelationships, between states. Processes 5 and 7 each represent stepstaken after demolding of a lens. The lens has an initial demoldtemperature indicated as demold temperature 4.

A first process 5 includes a conventional air cool process 5 a. Afterremoval from a mold, the lens is cooled to room temperature in anambient air environment. Once room temperature is achieved, the lens isrinsed 5 b, preferably in alcohol and air-dried at 5 c. Next, theair-dried lens is dip coated at point 6 and finally cured.

A second process 7 includes a conventional liquid cool process 7 a. Thisprocess is disclosed in U.S. Pat. No. 6,024,902 to Maus et al. Afterremoval from a mold, the lens is destaticized and cooled to roomtemperature in an alcohol bath. Once room temperature is achieved, thelens is air-dried 7 b for a period and may require a cleaning process (7c) with an additional air dry step (7 d). Next, the air-dried lens isdip coated at point 8 and finally cured. As a result of static chargebuild-up on the lenses, particulate matter is attracted to the lensespecially during air-drying. Referring to FIG. 2, static charge on thelenses is reduced by dipping the lenses in one or more baths. FIG. 2comparatively shows static charge in the lenses during processes 5 and7. Particulate matter, such as dust, or other air-borne particles, maybe deposited on the lens when exposed to air. Although filtered airsystems maybe employed, particulate matter is still a threat to lensesexposed to air.

Therefore a need exists for an automated lens dipcoating process, whicheliminates or significantly reduces drying times in air during theprocess. A further need exists for reducing the amount of exposure timeto particulate matter in air especially when a static charge is presenton a lens.

SUMMARY OF THE INVENTION

A method of decreasing the time between de-molding a lens and initiatinga hard coating process, in accordance with the present invention,includes the steps of transporting the de-molded lens at a de-moldtemperature T_(M) away from a mold, maintaining a dip tank to atemperature T_(D), where T_(D) is less than T_(M), wherein the dip tankincludes a liquid including one of a primer and a hard coat solution,and dipping the lens into the dip tank wherein the lens has atemperature T_(L) greater than T_(D), so that intermediate cooling,cleaning, destaticizing and delays associated therewith are avoided.

A method of decreasing the time for dipcoating a lens, in accordancewith the present invention includes the steps of drying thermoplasticraw material in advance of molding an article, molding the article, anddipping the article while the article is at a temperature greater thanthe ambient temperature in a dip tank including a primer solution,wherein the primer in the solution has a concentration of less than 10%by volume.

Other methods eliminate many conventional process steps and may includedrying raw material to decrease primer coating times and employingrobotic systems for carrying out the methods. The illustrativeembodiments of the present invention should not be construed as limitingthe present invention as presented in the appended claims.

A method of hard coating a lens includes maintaining a dip tank at atemperature T_(D), wherein the dip tank includes a liquid including aprimer or a hard coat solution. The lens is dried and heated to atemperature. T_(L) within 20 degrees F. of T_(D). The lens is dippedinto the dip tank wherein T_(L) is greater than T_(D).

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages, nature, and various additional features of the inventionwill appear more fully upon consideration of the illustrativeembodiments now to be described in detail in connection withaccompanying drawings. In the drawings wherein like reference numeralsdenote similar components throughout the views:

FIG. 1 is a graph comparing temperature vs. time for two prior artpreparation processes before dip coating lenses for in-linemanufacturing of prescription lenses in accordance with the prior art.

FIG. 2 is a graph comparing static charge vs. time for two prior artpreparation processes before dip coating lenses for in-linemanufacturing of prescription lenses in accordance with the prior art.

FIG. 3 is a flow chart of steps for dipcoating a lens.

FIGS. 4A and 4B show lens configurations after molding in accordancewith one aspect of the present invention.

FIG. 5 is a chart comparing dip coating process start times for the twoprior art processes shown in FIGS. 1 and 2 and the process in accordancewith the present invention.

FIG. 6 is a schematic diagram showing a system for in-line manufacturingof prescription lenses in accordance with the present invention.

FIG. 7 is a flow chart of steps for another embodiment for dipcoating alens.

FIG. 8 is a schematic diagram showing another embodiment of a system forin-line manufacturing of prescription lenses in accordance with thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides methods for dipcoating lenses in anefficient manner, which eliminate or reduce process steps and reduceyield loss due to long duration air drying or air cooling steps. In oneembodiment of the present invention, systems and methods advantageouslyemploy an automated robotic system to remove plastic lenses from aninjection or compression mold and transfer the lenses to dippingstations. The lens is optionally dipped in a primer solution. Next, thelens is rinsed in a solvent solution and then dipcoated. The methodincludes transferring the lenses from the mold to dipping stations, anddipping the lens in a primer solution while the lens is still hot. Thedipping into the primer solution destaticizes the lens and reduces itstemperature. Next, while the lens is still hot, the lens is transportedto a rinsing station where it is dipped without drying the lens. Thelens is then removed from the rinse bath, subjected to a forced air jetand dipped into a dip coating solution. Advantageously, the lens is notexposed to ambient air between the demold step and the dip coat step formore than a few minutes, and preferably less than 5 minutes. Thissignificantly reduces the risk of particulate deposition on the lens.

Contrary to the prior art, the lens is dipped and processed while it ishot. The molding material employed in the process is preferablysubjected to a drying process before being used in the mold. Inaccordance with the present invention, by reducing the moisture in theraw material before molding, solvent attack on the lens material isminimized. Advantageously, the lens can be processed hot, therebyreducing air cool and air dry times significantly and/or eliminating aircool or air dry times completely from the process.

It is to be understood that the parameters, such as dipping speeds andtemperatures may be adjusted or arbitrarily set in accordance withdifferent aspects and applications of the present invention. It isfurther to be understood that process steps as set forth in the FIGs.may be performed by robots programmed by software or performed directlyby software, hardware or a combination therefore. Software programs maybe carried out on a processor or processors, including memory andappropriate interfaces for performing system functions and method stepsin accordance with the present invention.

Referring now in specific detail to the drawings in which like referencenumerals identify similar or identical elements throughout the severalviews, and initially to FIG. 3, a flow/block diagram for a method fordipcoating a lens is illustratively shown. In block 8, a drying step isperformed on virgin molding materials. Molding materials preferablyinclude polycarbonate although other suitable thermoplastics may beemployed. Drying may be performed immediately prior to placing thethermoplastic into a hopper or feed to the molding process (block 10) ordrying may be performed at an earlier time and the thermoplastichermetically sealed to prevent moisture from being absorbed in thethermoplastic. In one particularly useful embodiment, raw material, suchas pellets of polycarbonate, are dried by exposing the material to anenvironment with a dew point temperature of −40 degrees F. or less forabout 2-4 hours. Other drying methods, dew point temperatures and dryingtimes may also be used.

It is preferable that moisture present in the thermoplastic material bereduced as much as possible. Thermoplastics, such as polycarbonate canabsorb enough moisture to impact its processing in as little as a fewminutes. A correlation between drying the raw material and the bondingeffectiveness of a primer material to plastic lenses has beendetermined. Drying (or pre-drying) in block 8 is therefore preferableespecially when high throughput dipping is desired. High throughput isprovided, among other things, by reduced dipping dwell times, byproviding the capability of dipping hot lenses, by eliminating dryingsteps required by the prior art, etc.

In block 10, a molding process is performed to form a lens, a pair oflenses or multiple pairs of lenses. The molding process may include aplastic molding process, such as an injection or compression moldingprocess, and form stems or other features, which may be employed to holdand transport the lenses. In block 12, the lenses (or lens) are removedfrom the mold. This may be performed in a plurality of different ways.One skilled in the art would understand that pushpins or pneumaticdrivers may be employed to remove a lens along with sprues and/or gatedmaterials from the mold. The molding process is preferably an automatedmolding process, which includes, for example, a pneumatically orhydraulically actuated split half mold system. A mold temperature/lenstemperature at the time of demolding may be about, e.g., 250 F to about300 F. A de-mold temperature T_(M) begins to drop after de-molding.

In block 14, a take-out robot removes the molded lens from the moldingsystem and transports the lens to a degate station, if needed. At thedegate station, the sprues and/or gated materials are removed from thelens with high efficiency particulate arresting (HEPA) downdraft tocontrol/eliminate dust due to the cutting/degate process. The degate maybe performed by employing cutters, such as pneumatic cutters. Degatingmay not be needed since molds and molding processes are contemplatedwhich produce ready-for-dipping lens structures. These structures mayinclude gated materials; yet need not be degated until later in theprocess. Cold-runners disposed between two or more lenses may becut/degated by cutters. The cutters are preferably maintained in anenvironment that employs a high efficiency particulate arresting (HEPA)air curtain or downdraft airflow to reduce air borne particles, whichmay be generated, by the cutters or be present in the enclosure.

The transport of the lens preferably occurs in a reduced humidityenvironment, e.g., 15% relative humidity or less. The reduced humidityenvironment is preferably heated and maintained in a temperature rangefrom about 90 degrees F. to about 110 degrees F. The environmentpreferably includes a high efficiency particulate arresting (HEPA)filtered environment.

In block 16, a take-out robot preferably transfers the lens or lenses toa transfer robot. A single robot may perform both take-out and transfertasks. Alternately, a worker or technician may transfer the lens fromthe mold to the transfer robot. The transfer robot then orients the lensinto a dipping position. This is preferably in a vertical orientation,that is, the major plane of the lens is held in a substantially parallelorientation relative to the vertical direction.

In block 18, the transfer robot moves the lens to a first dippingstation. It is noted that the lens may still be at an elevatedtemperature, such as the mold temperature. A dip tank is preferablyheated to a temperature T_(D), where T_(D) is less than T_(M). The diptank preferably includes a primer or a hard coat solution.

The lens is dipped into a liquid at the first station. In oneembodiment, this first station includes a primer, preferably with aconcentration of less than 10% by volume, and more preferably less than5% by volume, and even more preferably less than 2% by volume. By thepresent invention, primer concentrations of about 0.5% by volume may beachieved based on the moisture content of the raw materials used in themolding process. A primer may be employed to provide a layer ofmaterial, which assists in transitioning the surface to permit adhesionof an inorganic dipcoat to the organic material of the lens. The primermay include for example, an amino-silane primer. Other primers are alsocontemplated.

By providing dried thermoplastic to the molding process, outgassing ofmoisture is reduced or eliminated. Outgassing of moisture can preventthe formation of a primer-to-thermoplastic bond. Advantageously, byreducing the moisture content and reducing outgassing, a hot or highertemperature lens in the process of cooling would still providesufficient bonding of primer to the lens.

In addition, since pre-drying reduces outgassing, the surface of thelens is more receptive to primer bonding even while the lens is coolingdown. This is in contradiction of the prior art, which requires the lensto be cooled to room temperature prior to applying a primer.

One result of the method of the present invention is that theconcentration in the primer bath may be reduced to say 2% or less andstill have uniform coverage of one or more monolayers of primer. Theprior art requires a primer concentration of about 10% or greater byvolume. In addition, the primer coating process of the present inventionis more efficient requiring less time to primer coat the lens and lesstime to rinse (to dissolve excess primer) in subsequent rinse steps.

Dipping the lens at the first station is preferably performed without alarge amount of splashing, and air bubbles are to be avoided since theymay be the source of later problems resulting in the rejection of thelens. The lens is completely submerged in the bath to ensure completecoverage and remains in the bath, for example, for about 30 seconds. Thelens preferably has a temperature T_(L), which is greater than T_(D), sothat intermediate cooling, cleaning, destaticizing and delays associatedtherewith are avoided. The dip tank, which includes primer, preferablycontains below a 2% concentration of primer, and more preferably below a1% concentration of primer. The dip tank is preferably heated within arange from about 100 degrees F. to about 150 degrees F. (which is thetemperature T_(D))

By dipping the lens in a primer or hard coat solution while the lens isstill hot, many process steps employed by conventional techniques areeliminated. These steps include but are not limited to cooling the lens,cleaning the lens in detergents and rinse baths, destaticizing steps andrelated activities. In accordance with the present invention, it hasbeen discovered that by reducing or eliminating moisture in the lensmaterial in advance of primer dipping permits low concentration primersolution usage as well as the ability to dip the lens while it is stillhot. Also, heating the dip bath to an elevated temperature (preferablyabove room temperature) permits a hot lens to be dipped with reducedlikelihood of solvent attacks previously feared in conventionaltechniques. In addition, by providing a “hot dip,” hours ofmanufacturing delays are avoided and considerable cost savings arerealized.

In block 20, the lens is removed from the dip bath. The dipping step mayinclude evening out the thickness of the primer by further dipping thelens in a rinse tank in block 22. The primer and the rinse may include awater-based primer and a water-based rinse, respectively. The lens orlenses are submerged in the rinse bath for a predetermined amount oftime so that the rinse bath dissolves away some of the primer to createan even thickness of at least a monolayer of primer over the lens.

It is noted that the configuration for supporting the lens is oneimportant factor in the yield of the process. Each lens should besupported at its periphery at a location below the horizontal centerlineof the lens when held in the dipping position. In one embodiment, thelens is supported by a stem or gated material, which is integrallyformed with the lens and connects to the lens, preferably between a 3o'clock and a 9 o'clock position. During a dipping process, anystructure for holding the lens, which is above the horizontalcenterline, could result in liquid collecting on the structure. Thiscollected liquid runs down onto the lens and causes streaks. Thesestreaks may result in the lens being rejected. FIG. 4 illustrativelyshows illustrative configurations for supporting a lens. FIG. 4 will bedescribed in greater detail below.

The rinse station may include water, an alcohol, a ketone or any othersolvent. In a preferred embodiment, the rinse bath includes water, andpreferably deionized water. If a primer is not needed then the firststation includes this rinse bath and the primer bath is omitted from theprocess. In one embodiment, which employs primer, the solvent of thebath dissolves the primer to reduce the thickness of the primer. It ispreferable that only a thin layer of primer exists on the lens, and morepreferably that a monolayer of primer be present. The water in the rinsebath dissolves the primer for a predetermined amount of time to reducethe amount of primer present on the lens, e.g. reduce the primerthickness to about a monolayer. The rinse bath preferably includes thesame base solvent of the primer solution. It should be noted that thelens may still be in a state of elevated temperature prior to beingimmersed in the bath at the second or third station.

When the lens is immersed into the second bath (e.g., a rinse bath), thelens is completely submerged and may be maintained in an immersed statefor a predetermined amount or time, e.g., tens of seconds. The rinsebath may be adjusted to optimize the state of the liquid, for example,reduce an agitation frequency of a bath agitator during the immersion.

In block 24, the lens is transferred to a dipcoating station. Thedipcoating station may include heat/infrared curable coatings or UVcurable coatings. With UV curable coatings, the primer station may beeliminated from the process sequence. The lens is lowered into the bath.

In block 26, after dipcoating, the lens is transferred to a curing lineto be pre-cured. In block 28, after pre-curing, the lenses mayoptionally be inspected. For example, a visual inspection may beperformed to determine flaws or cosmetic failures. Then, in block 30, afull cure may be performed. The curing line may include one or more ofheating lamps, infrared radiant heaters and/or UV light sourcesdepending on the type of coating employed. The curing is also preferablymaintained within the same enclosure as the other process steps.

In block 32, an inspection is performed to look for cosmetic failures,such as streaks, dirt, smudges, lens flaws, etc. Lenses that do not meetthe inspection criteria are rejected or set aside for possible rework.Lenses that meet the inspection criteria may be secondarily degated orotherwise prepared for packaging and/or shipment.

Referring to FIGS. 4A and 4B, illustrative lens arrangements are shownwhich are particularly useful in accordance with the present invention.Each lens 50 connects to a gated stem 52. Stem 52 is preferably formedduring the same molding process that forms the lens 50. Stem 52 mayinclude gripping positions 54 and 56, which may be employed to permitlens transfer between stations or robots. Gripping positions 54 and 56may be employed as locations where a robot or robots grip assemblies 58and 60, and are particularly useful for transferring lenses betweenrobots. Gripping positions 54 and 56 may include a plurality of elementsfor securing or interfacing with specific robotic features. Assembly 58includes a single lens 50 while assembly 60 includes a pair of lenses50.

Referring to FIG. 5, a bar chart indicating relative times before lens adip coating process may be undertaken is illustratively shown. In afirst prior art process 5, upon demolding, a lens is air cooled to roomtemperature (Air Cool 5 a). After air cooling, the lens may be dipped indetergent and rinsed (Rinse 5 b). The rinse process may include a seriesof detergent/rinse baths in which the lens is serially dipped. After thecleaning process, the lens is air dried (Air Dry 5 c). This process mayinclude exposing the lens to an elevated temperature environment untilthe lens is completely dried. Once dried, the lens dip coating proceduremay begin at point 61.

In a second prior art process 7, upon demolding, the lens isdestaticized and cooled in an alcohol bath (Liquid Cool 7 a). Afterreaching, room temperature (bath temperature), the lens is removed fromthe bath and air-dried (Air Dry 7 b). Next, to remove the alcoholresidue, the lens is rinsed (Rinse 7 c) and air-dried again (Air Dry 7d). The rinse step may include multiple detergent and rinse processes,as stated above. At point 62, the dip coating processing begins.

In accordance with the present invention, dip coating or primerapplication (i.e., the dip coating process 3) begins immediately afterdemolding (or perhaps after primary degating) of the lens or lenses.FIG. 5 demonstrates a significant advantage of timesavings due to thehot dip process 9 of the present invention. Advantageously, hours ofprocessing time are reduced or eliminated from the process sequencesince air or liquid cool down times are avoided. Furthermore, thepresent invention eliminates detergent and rinse steps and associateddrying times which are required for prior art processes.

Referring to FIG. 6, an in-line assembly tool 100 is illustrativelyshown in accordance with one embodiment of the present invention. Adrying station 101 may be included to dry out thermoplastic rawmaterials before molding. Drying station 101 may include a low humiditychamber and/or a temperature controlled chamber for maintaining a dewpoint temperature at the desired level for a period of time. A moldingunit or units 102 may include split-half molds 104 a and 104 b, whichperform, for example, injection or compression molding. The moldingcycle includes closing the mold, heating the mold to a giventemperature, and injecting molten plastic into the mold. The mold iscooled and the part (e.g., the lens, pair of lenses or multiple pairs 6f lenses) is extracted from the mold by a take-out robot 106. Theplastic part remains hot and is transferred by robot 106 to a degatingstation 108. A cutter 110, for example, a pneumatic cutter may beemployed to remove any sprues or gated material from the lenses.

The takeout robot 106 transfers the lens to a first station 112 fordipping. The first station 112 may include a hard coat station or aprimer station. A lens 114 may be transferred to a transfer robot 116 todip the lens. In an alternate embodiment, the take-out robot 106 and thetransfer robot 116 are the same. Robot 106 or 116 positions lens 114over a bath 118 at station 112. As described above, lens 114 is immersedin the liquid of first station 112 while at an elevated temperature, andthen the lens 114 is removed from the bath of first station 112 by robot116. Depending on the process speed, the shape and volume of the lensand the temperatures of the bath and ambient environment, the lenstemperature T_(L) may be maintained at or below the demold temperatureT_(M), but greater than room or ambient temperature.

The lens 114 may still have an elevated temperature before dipping thelens 114 into a second or more baths. In other words, a lens could behot dipped at a first station, remain hot and be transported and dippedat a second station, and so on. Prior art processes required cooling thelens to room temperature before any dipping coating process steps werebegun.

At a second station 122, a bath 123 may include a rinse solvent, such aswater, alcohol, a ketone, etc. or a hardcoat liquid. For example, if thefirst station 112 includes a water-based primer, water is preferablyemployed in the bath at station 122, more preferably deionized water. Inthis case, station 122 is a rinse station which assists is dissolvingaway some of the primer coat applied at station 112. If a primer coat isnot needed station 112 may be eliminated from system 100, and a suitablesolvent may be selected for station 122. It is preferable to employwater, however, since alcohols or ketones may be flammable, and may posehealth or safety concerns. Additional dipping stations may also beemployed and be part of the dip coating process.

It is to be understood that multiple lenses may be processedconcurrently. This means that each bath may receive one or more lensessimultaneously to increase throughput. Lenses at each station may belowered and raised concurrently and then advanced to a next station toprovide a constantly progressing manufacturing line.

Next, lenses 114 are transported to a dip coating station 124, submergedin a bath 125 of dip coat or hardcoat material and then removed frombath 125.

Once the dipcoat has been applied, the lens 114 is transported to apre-cure station 134. Pre-cure station 134 heats the lenses to begin thecuring process. Pre-cure station 134 cures the dipcoat to a tacky stateso that a visual inspection at station 135 may be performed. The visualinspection eliminates from the manufacturing line lens failures, whichcan be identified early in the curing process. By inspecting the lensesafter a pre-cure, further expense, resources and process time are savedby taking lenses which are recognized early as failures out of the line.Further energy (and curing time) is not expended on these known rejects.The rejected lenses may be salvaged for rework. The visual inspectionprocess may include passing each lens in front of a light to inspect forcosmetic defects, structural defects, and/or contamination due toforeign particles, etc. After the optional inspection process, thelenses are transported to a curing station 138 and passed through anoven or other heat source to provide a full cure of the dipcoat.

After curing, additional inspections may be performed to determine thequality of the lenses output from system 100. These may includeautomatic (computer-based) inspections or manual inspections.Additionally, secondary degating, packaging or any other post processingsteps may be performed.

To increase yield it is advantageous that the process be performed in asingle enclosure 150. Enclosure 150 may include a clean room environmentor an isolated enclosure. Enclosure 150 is preferably maintained atconstant or near-constant conditions. For example, to promoteevaporation of water from the lenses after rinse station, low humidityand high temperature are preferred. In one embodiment, relative humiditymay be maintained at or below, for example, 15% while the temperaturemay be maintained at or above, for example, 96 degrees F.

Particulate matter may be filtered from the ambient air by employing anair filtration system 144. Filtration system may include, for example, aHEPA filtration system and more preferably a class 10 or better HEPAfiltration system. In this way, air borne particles are removed and therisk of particulate contamination of the dipcoated lenses is reduced.

Referring now to FIG. 7, a flow diagram showing an alternate embodimentof the present invention is illustratively shown. In block 310, amolding process is performed to form a lens, a pair of lenses ormultiple pairs of lenses. The molding process may include a plasticmolding process, such as an injection or compression molding process,and form stems or other features, which may be employed to hold andtransport the lenses. These lenses may be formed from, for example,polycarbonate or similar plastics. In block 312, the lenses (or lens)are removed from the mold. This may be performed in a plurality ofdifferent ways. One skilled in the art would understand that pushpins orpneumatic drivers may be employed to remove a lens along with spruesand/or gated materials from the mold. The molding process is preferablyan automated molding process, which includes, for example, apneumatically or hydraulically actuated split half mold system. A moldtemperature/lens temperature at the time of de-molding may be about,e.g., 250 F to about 300 F. A de-mold temperature T_(M) begins to dropafter de-molding. In this embodiment, a plurality of molding devices maybe employed which feed into a dipcoating apparatus or are cached in astorage area until a later time. Such a storage area is preferably in aclean room environment and/or with little, and preferably with little orno humidity present. Alternately, storage may be maintained under normalambient conditions; however, further processing may be needed prior todipcoating.

In block 314, a take-out robot removes the molded lens from the moldingsystem and transports the lens to a degate station, if needed. At thedegate station, the sprues and/or gated materials may be removed fromthe lens with high efficiency particulate arresting (HEPA) downdraft tocontrol/eliminate dust due to the cutting/degate process. Degating maynot be needed since molds and molding processes are contemplated whichproduce ready-for-dipping lens structures. These structures may includegated materials; yet need not be degated until later in the process.Cold-runners disposed between two or more lenses may be cut/degated bycutters. The cutters are preferably maintained in an environment thatemploys a high efficiency particulate arresting (HEPA) air curtain ordowndraft airflow to reduce air borne particles, which may be generated,by the cutters or be present in the enclosure.

The transport of the lens may occur in a reduced humidity environment,e.g., 15% relative humidity or less. The reduced humidity environment ispreferably heated and maintained in a temperature range from about 90degrees F. to about 110 degrees F. The environment preferably alsoincludes a high efficiency particulate arresting (HEPA) filteredenvironment.

In block 315, a take-out robot preferably transfers the lens or lensesto a transfer robot. A single robot may perform both take-out andtransfer tasks. Alternately, a worker or technician may transfer thelens from the mold to the transfer robot. The transfer robot may placethe lens or lenses on a storage rack or other storage device in block316.

At a later time or while still hot from the mold, the lens or lenses aresubjected to a drying or drying/heating process to prepare the lensesfor dip coating in block 317. If the lens has been stored a cleaningprocess may be performed. The drying step may be performed immediatelyafter demolding the lens or by placing the lens into a dry environmentfor a predetermined time prior to dipcoating. The drying process cansimultaneously remove cleaning solvents or solutions and any accumulatedmoisture. In one particularly useful embodiment, the lenses ofpolycarbonate may be maintained in storage and dried by exposing thematerial to an environment with a dew point temperature of −40 degreesF. or less for about 2-4 hours. Other drying methods, dew pointtemperatures and drying times may also be used.

It is preferable that moisture present in the thermoplastic material bereduced as much as possible. Thermoplastics, such as polycarbonate canabsorb enough moisture to impact its processing in as little as a fewminutes. Drying (or pre-drying in block 8 FIG. 3) may be employed incombination. Drying may also be achieved by storing or passing thelenses through a low humidity elevated temperature environment. Forexample, an ambient temperature in an enclosed clean environment leadinginto a dipcoating area may be provided. This temperature is preferablywithin 20 degrees of the dipcoating primer bath, and more preferablywithin 10 degrees of the dipcoating primer bath. The humidity maypreferably be maintained at or below 15%.

After drying or drying/heating, the transfer robot transports the lensand orients the lens into a dipping position. This is preferably in avertical orientation, that is, the major plane of the lens is held in asubstantially parallel orientation relative to the vertical direction.In block 318, the transfer robot moves the lens to a first dippingstation. It is noted that the lens is at an elevated temperature, T_(E),as a result of the heating process or T_(M) (or less) as a result of themold temperature. A dip tank is preferably heated to a temperatureT_(D), where T_(D) is less than T_(M). T_(E) is preferably less thanT_(M) and preferably within 20 degrees F. of T_(D). The dip tankpreferably includes a primer or a hard coat solution.

The lens is dipped into a liquid at the first station as describedabove. In one embodiment, this first station includes a primer,preferably with a concentration of less than 10% by volume, and morepreferably less than 5% by volume, and even more preferably less than 2%by volume. By the present invention, primer concentrations of about 0.5%by volume may be achieved based on the moisture content of the rawmaterials used in the molding process. A primer may be employed toprovide a layer of material, which assists in transitioning the surfaceto permit adhesion of an inorganic dipcoat to the organic material ofthe lens. The primer may include for example, an amino-silane primer.Other primers are also contemplated.

By providing pre-dried thermoplastic, outgassing of moisture is reducedor eliminated. By drying before dipcoating, moisture buildup can beprevented which can thwart the formation of a primer-to-thermoplasticbond. Advantageously, by reducing the moisture, a hot or highertemperature lens would provide sufficient bonding of primer to the lens.Processing proceeds in blocks 320-332 as described above for blocks20-32 with reference to FIG. 3.

Referring to FIG. 8, molding units 302 may include split-half molds,which perform, for example, injection or compression molding. Themolding cycle includes closing the mold, heating the mold to a giventemperature, and injecting molten plastic into the mold. The mold iscooled and the part (e.g., the lens, pair of lenses or multiple pairs oflenses) is extracted from the mold by a take-out robot. FIG. 8 shows aplurality of molding devices feeding a single manufacturing queue 301.The queue 301 feeds into a storage system 303 or directly into adrying/heating area 304, where the lenses are prepared for dip coatingat dipping stations 306.

The storage area 303 may include racks or other storage means capable ofholding lenses or pairs of lenses while permitting access to grippingpositions for transfer robots or manual operators to grip and pass thelenses to a next manufacturing station. Storage area 303 may bebypassed, permitting lenses in queue 301 to go directly todrying/heating station 304.

While in queue 301 different process steps may be performed, preferablyin a humidity controlled clean room environment. For example, transferby robots may carry demolded lenses to a degating station, where forexample, a pneumatic cutter may be employed to remove any sprues orgated material from the lenses. In one embodiment, relative humidity maybe maintained at or below, for example, 15% while the temperature may bemaintained at or above, for example, 96 degrees F. in queue area 301.

If the lenses are stored a cleaning process may be employed. Storagearea 303 may include a drying station to dry out thermoplastic lensmaterials before dipcoating. The drying station may include a lowhumidity chamber and/or a temperature controlled chamber for aintaininga dew point temperature at the desired level for a period of time.Drying may include removing residual cleaning solvents and any moisture.The drying/heating station preferably prepares the lens for dipcoatingby elevating a temperature of the lens to within 20 degrees F. of thebath temperature of a primer bath. It is preferable that the lenstemperature exceeds the bath temperature within a 20 degree F., and morepreferably within a 10 degree F. difference.

The takeout robot transfers the lenses to dipping stations 306. Dippingstations 306 preferably include the setup set forth with reference toFIG. 6. As described above with reference to FIG. 6, lens 114 isimmersed in the liquid of first station 112 while at an elevatedtemperature, and then the lens 114 is removed from the bath of firststation 112 by robot 116. The lens temperature T_(L) is provided andmaintained at or above the bath temperature of first station 112.

The lens 114 may still have an elevated temperature before dipping thelens 114 into a second or more baths. In other words, a lens could behot dipped at a first station, remain hot and be transported and dippedat a second station, and so on. Prior art processes required cooling thelens to room temperature before any dipping coating process steps werebegun.

It is to be understood that multiple lenses may be processedconcurrently. This means that each bath may receive one or more lensessimultaneously to increase throughput. Lenses at each station may belowered and raised concurrently and then advanced to a next station toprovide a constantly progressing manufacturing line.

After rinsing, lenses 114 are transported to a dip coating station 124,submerged in a bath of dip coat or hardcoat material and then removedfrom bath. Once the dipcoat has been applied, the lens processingcontinues as described above.

Having described preferred embodiments for in-line lens manufacturingmethods and systems (which are intended to be illustrative and notlimiting), it is noted that modifications and variations can be made bypersons skilled in the art in light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiments of the invention disclosed which are within the scope andspirit of the invention as outlined by the appended claims. Having thusdescribed the invention with the details and particularity required bythe patent laws, what is claimed and desired protected by Letters Patentis set forth in the appended claims.

1. A method of hard coating a lens, comprising the steps of: maintaininga dip tank at a temperature T_(D), wherein the dip tank includes aliquid including one of a primer and a hard coat solution; drying thelens; heating the lens to a temperature T_(L); dipping the lens into thedip tank wherein T_(L) is within 20 degrees F. of T_(D).
 2. The methodof claim 1, wherein the step of drying includes the step of storing thelens in a dry environment.
 3. The method of claim 2, wherein the dryenvironment is heated.
 4. The method of claim 2, wherein the dryenvironment is heated to a temperature within a range from about 90degrees F. to about 110 degrees F.
 5. The method of claim 1, wherein thestep of drying the lens is performed after the lens has been stored. 6.The method of claim 1, further comprising the step of molding the lenswherein the step of drying the lens is performed after demolding thelens.
 7. The method of claim 1, further comprising the step of predryingraw material, used for forming the lens, before introducing the rawmaterial into a mold.
 8. The method of claim 7, wherein the predryingstep includes maintaining the raw material in an ambient environmenthaving a negative dew point temperature.
 9. The method of claim 8,wherein the maintaining the raw material step includes maintaining theraw material in an ambient environment having a dew point temperature of−40 F for between about 2 hours and about 4 hours.
 10. The method ofclaim 1, wherein the dip tank includes below a 2% concentration ofprimer.
 11. The method of claim 1, wherein said dipping step comprisesdipping the lens into the dip tank wherein T_(L) is greater than T_(D).12. The method of claim 1, wherein the dip tank is heated within a rangefrom about 100 degrees F. to about 150 degrees F.
 13. The method ofclaim 1, wherein the dipping step includes a primer dip and the methodadditionally includes the step of: evening out the thickness of theprimer by further dipping the lens in a rinse tank.
 14. The method ofclaim 13, wherein the primer and the rinse comprise a water-based primerand a water-based rinse, respectively.
 15. The method of claim 1,wherein the steps of drying and heating are performed concurrently. 16.A method for dipcoating a lens, comprising the steps of: predryingthermoplastic raw material in advance of molding an article; molding thearticle; maintaining a dip tank at a temperature T_(D), wherein the diptank includes a liquid including one of a primer and a hard coatsolution; drying the lens; heating the lens to a temperature T_(L);dipping the lens into the dip tank wherein T_(L) is within 20 degrees F.of T_(D).
 17. The method of claim 16, wherein the dip tank includes aprimer solution, and the primer in the solution has a concentration ofless than 10% by volume.
 18. The method of claim 16, wherein the step ofpredrying includes maintaining the raw material in an ambientenvironment having a negative dew point temperature.
 19. The method ofclaim 18, wherein the step of maintaining the raw material includesmaintaining the raw material in an ambient environment having a dewpoint temperature of −40 F for between about 2 hours and about 4 hours.20. The method of claim 16, wherein the step of drying includes the stepof storing the lens in a dry environment.
 21. The method of claim 20,wherein the dry environment is heated.
 22. The method of claim 20,wherein the dry environment is heated to a temperature within a rangefrom about 90 degrees F. to about 110 degrees F.
 23. The method of claim16, wherein the step of drying the lens is performed after the lens hasbeen stored.
 24. The method of claim 16, wherein the predrying stepincludes maintaining the raw material in an ambient environment having anegative dew point temperature.
 25. The method of claim 24, wherein themaintaining the raw material step includes maintaining the raw materialin an ambient environment having a dew point temperature of −40 F forbetween about 2 hours and about 4 hours.
 26. The method of claim 16,wherein the dip tank includes below a 2% concentration of primer. 27.The method of claim 16, wherein said dipping step comprises dipping thelens into the dip tank wherein T_(L) is greater than T_(D).
 28. Themethod of claim 16, wherein the dip tank is heated within a range fromabout 100 degrees F. to about 150 degrees F.
 29. The method of claim 16,wherein the dipping step includes a primer dip and the methodadditionally includes the step of: evening out the thickness of theprimer by further dipping the lens in a rinse tank.
 30. The method ofclaim 29, wherein the primer and the rinse comprise a water-based primerand a water-based rinse, respectively.
 31. The method of claim 16,wherein the steps of drying and heating are performed concurrently.